Organ ensemble and reverberation system



June 11, 1963 1-. J. GEORGE 3,093,701

ORGAN ENSEMBLE AND REVERBERATION SYSTEM File July 17, 1959 3 Sheets-Sheet 1 1 1815201314 z [a I] 9 38 8 If I 7 2a 2 24A 25 2b 28 Fl q- A TTORNE V June 11, 1963 -r. J. GEORGE ORGAN ENSEMBLE AND REVERBERATION SYSTEM 3 Sheets-Sheet 2 Filed July 17, 1959 W T M m h= n Q N mumiu .m M02523 U28. k on v 29565 00 D. fi umwag lul 2435 m a r w n m\ Q Q Q E m hm m m J m9 w W I a". I @v n# on 3 no mm mm m 1 Mn ii +n w 1 m 8 m E m 91m an 1F 3 3 mm QoNIHI \m .nm.\ mm um m N +0 w 0N m IIIV $592 S KE i j ATTORNEY June 11, 1963 T. J. GEORGE ORGAN ENSEMBLE AND REVERBERATION SYSTEM Filed July 17, 1959 3 Sheets-Sheet 3 FIG. 6

ORGAN AHPLI FIER TONE eemuamoe J 9 7 m a F 8 R M A 5 m. 7 v J zs A P M A w u an 0| F United States Patent OfilCfi Patented June 11, 1963 3,093,701 ORGAN ENSEMBLE AND REVERBERATION SYSTEM Thomas J. George, 11671 Victory Blvd., North Hollywood, Calif. Filed July 17, 1959, Scr. No. 827,898 21 Claims. (Cl. 841.24)

The present invention relates in general to electronic organs, and more particularly to new and improved means for the enhancement of the tones produced by an electronic organ.

The electronic organ has now become a serious musical instrument in its own right. Its rising acceptance has largely been due to two factors; first, it is capable of pro ducing pleasing sustained tones somewhat similar to the tones produced by a pipe organ, and second, it is much less costly to manufacture than a pipe organ. There are, however, at least two areas where present day electronic organs fail to emulate the desirable musical effects produced by a pipe organ.

A first one of the areas in which known electronic organs are deficient is the production of musical ensemble or chorus, which is the full rich musical effect obtained when many instruments are played together, as in a symphony orchestra or in a large pipe organ, when many ranks of pipes are played together. The effect arises from the fact that when two or more instruments or pipes are played together they are generally slightly out of tune with one another. The result is that when the same musi cal note is played simultaneously, a slight beating or undulation of the combined tone occurs which is very pleasing to the ear of a listener. This undulation or rise and fall of the tone is absent when a single instrument or pipe is played alone. It is, therefore, more pleasing when a number of instruments or a number of ranks of organ pipes are played together. The beating producing a musical ensemble or chorus efi'ect occurs because the phase differences of the tones produced by two or more instruments or pipes at any given instant combine vectorially, thus causing the composite tone to become louder and softer. It should also be noted that where the two instruments or pipes are separated in space, and the tones are not coming from a single point source such as the speaker of an electronic organ, the vector combinations of the tones will not be the same in both cars at any given instant, and as the vector relationship changes, there will be a pleasing three dimensional or stereophonic feeling observed by the listener, as a certain spatial movement is seemingly imparted to the tones. As more instruments or organ pipes are added to the ensemble, the musical effect becomes richer, and the random pattern of the beats becomes very complex, enhancing still more the tones being played.

A basic goal in electronic organ design, especially in instruments intended for use in the home. is economy of construction. Therefore, it is customary in instruments of this type to provide no more than one separate tone generator or oscillator for each musical note of the organ, and only one amplifier and speaker system for the entire organ. Thus, in most present day electronic organs the major requirements for producing a musical ensemble effect are lacking since there can be no beating when a note is played when only one tone generator is provided and since there can be no spatial or stereophonic effect where only one speaker, or sound source, is employed. Even if two or more speakers are provided, the ensemble effect is still not obtained Where only one tone generator is utilized because the phase relationship of the tones coming from the speakers does not change. Accordingly, electronic organs normally lack the important pitch and spatial movement of tone, normally observed in an orchestra or pipe organ.

The second area where known electronic organs generally fall short of a pipe organ is that of reverberation. Traditionally we have come to associate reverberation with the music of the pipe organ because a pipe organ is usually installed in churches, cathedrals, auditoriums and other acoustically reverberant chambers. Many electronic organs are now being installed in homes, where the rooms are usually not reverberant. Rcverberation and ensemble are greatly needed in electronic organ installations in nonreverberant rooms. Reverberation is needed because it actually contributes to the ensemble, because of its traditional association with organ music, and because it actually makes it easier to play the organ, since it tends to fill the gaps between successive notes being played. Reverberation adds a feeling of bigness and grandeur to the tones of the electronic organ, to more nearly approach the tonal elfects of the pipe organ.

It has long been know that an artificial reverberative effect could be obtained by the use of the delay obtainable with a magentic wire or tape recorder. For example, multiple pick up heads are employed to obtain a series of delayed echoes derived from a magnetic wire recording. For the purpose of this disclosure, echo is defined as one acoustic reflection of the sound, and reverberation as a series of acoustic echoes, closely spaced in time, and of diminishing intensity. In another system a reentrant loop type of electronic circuit has been used for obtaining multiple echoes with a single delay mechanism in which a signal is recirculated around a circuit loop. However, neither of the above described arrangements is capable of providing an organ ensemble and reverberation device which enhances the tones of the electronic organ. Furthermore, there are a number of costly and complex tape operated reverberation arrangements now used for radio and recording purposes, but such arrangements are not suitable for incorporation in a low cost electronic organ for home use.

Accordingly, a principal object of this invention is to provide a low cost magnetic tape mechanism capable of producing artificial reverberation in an electronic organ.

Another object of the invention is to provide a device which imparts ensemble to the tones of an electronic organ.

Still another object of the invention is to provide new and improved means for stereophonic reproduction of organ tones from an organ having but one tone generating source for each musical note of the instrument.

Yet another object of the invention is to provide means for obtaining true stereophonic ensemble, and true stereophonic reverberation in the tones produced by an electronic organ.

An additional object of the invention is to employ ordinarily unwanted variations in tape speed of a magnetic tape recorder in a fashion which contributes to the ensemble elfect provided by an electronic organ.

It is still another object of the invention to provide a magnetic tape operated self teaching device for use in an electronic organ.

It is a further object of the invention to provide means for obtaining percussion effects from an electronic organ, not equipped to produce such effects.

In accordance with one aspect of the present invention, a system is provided for generating artificial reverberation and ensemble effects in an electronic organ including a recording arrangement in which a record head and a plurality of pickup heads are arranged along the length of a moving record medium. Signals d i d f a tone generator in the organ are reproduced without recording in one channel and in a second channel are recorded on the record medium via the record head. Delayed signals of varying phase relationship are derived from the record medium by means of the plurality of pickup heads and are combined for reproduction.

In one particular arrangement, signals derived from the pickup heads are fed back to the record head to establish a reentrant loop within which the signals recirculate, with means being provided for controlling the amount of attenuation during recirculation so that the time required for a given signal to die away may be set to achieve a desired effect. Each of the several pickup heads is suitably spaced along the record medium to achieve a desired phase relationship between the signals which contributes to the overall musical effect.

Further, a record medium transport system is arranged so that variations in velocity of the transport of the record medium produce desirable musical effects. In one embodiment of the invention, the delayed signals from the pickup heads are reproduced in a separate channel from the channel in which the signals derived directly from the tone generator are reproduced so that a stereophonic effect is achieved.

Furthermore, switching means may be included in accordance with another aspect of the invention by means of which the recording arrangement may be employed as a self teaching device.

In accordance with alternative arrangements of the invention, the recording device is adapted to produce special vibrato and c-eleste effects, along with the aforementioned ensemble and reverberation elfects which may be utilized separately or in combination with two separate channels for stereophonic reproduction.

In accordance with a still further aspect of the invention, tonal sustaining effects may be achieved by the use of a recording arrangement including record and pickup heads arranged along the length of a moving record medium.

A better understanding of the invention may be had from a reading of the following detailed description, taken in connection with the accompanying drawings, wherein:

FIG. 1 is a plan view of the physical arrangement of one form of the magnetic tape mechanism and the associated electronic parts in accordance with the invention;

FIG. 2 is a side view of the arrangement of FIG. 1, in which the electronic components have been omitted for the sake of clarity;

FIG. 3 is a bottom view of the arrangement shown in FIGS. 1 and 2;

FIG. 4 is a combined block and schematic circuit diagram of an electronic organ including associated ensemble and reverberation circuits in accordance with the invention;

FIG. 5 is a diagrammatic illustration of an electronic organ showing one physical arrangement of the related parts in one form of the invention;

FIG. 6 is a diagrammatic illustration of an organ showing an alternative arrangement of the related parts;

FIG. 7 is a diagrammatic illustration of an electronic organ in which part of the apparatus shown within the organ in FIGS. 5 and 6 has been installed in a separate tone cabinet;

FIG. 8 is a diagrammatic illustration of an electronic organ coupled to two separate tone cabinets;

FIG. 9 is a diagrammatic illustration of an electronic organ coupled to a tone cabinet of special design;

FIG. 10 is a diagrammatic illustration of a recording head and two pickup heads included for the purpose of explaining the production of ensemble effects in accordance with this invention; and

FIG. 11 is a diagrammatic illustration of a simplified form of an electronic organ in accordance with the invention in which a single amplifier and speaker are employed.

In FIG. 4, there is shown a combined block and schematic circuit diagram of an electronic organ including an ensemble and reverberation system in accordance with the invention. A tape magazine is indicated at 9 upon which an endless loop of magnetic recording tape 14 is stored. In operation, the tape moves continuously in the direction indicated by the arrows, around a pulley 16, past the erase head 15, a record head 18, and three pickup heads 19, 20 and 21. A high frequency oscillator 73 serves a dual function by supplying erase current to the erase head 15, and bias current to the record head 18. The use of bias currents in magnetic recording is well known in the art, and is described in US. Patent No. 2,351,004-Camras. The oscillator comprises two electron tubes 4 and 4' connected in a push-pull configuration. Both of the electron tubes may be enclosed within a single envelope, as for example, a tube type 12AU7. The plates of the electron tubes are connected to opposite ends of a primary winding 64 of a transformer 5. Operating potential may be supplied to the center tap of the winding 64 from a conventional D.-C. power supply, represented in the drawing by a B plus terminal 65, via a switch 83. The grids of the triodes are coupled to opposite terminals of the primary winding via the capacitors 68 and 69, and returned to ground via the grid resistors 70 and 72, respectively. The cathodes of electron tubes 4 and 4' are connected to a common cathode resistor 71. The winding 64 of the transformer 5 and a fixed capacitor 67 form a parallel resonant circuit which is tuned to a suitable frequency of oscillation, as for example, 50 kilocyclcs. A secondary winding 63 of the transformer 5 supplies erase current to the erase head 15 via a capacitor 62, and bias current to the recording head 18 via a capacitor 61. 4

An electron tube 3A which may be one of two triode sections in a dual section tube, such as type l2AU7, serves amplify the incoming signal from the organ as follows: The signal appearing at a pair of output terminals 74 and 75 associated with an electronic organ generator 82, is transmitted to an organ output amplifier 76 which drives a speaker 77 to produce an audible tone. The signal from the terminals 74 and 75 is also coupled to the grid of the electron tube 3A via a resistor 57 and a capacitor 56. A cathode resistor 58 returns the cathode of the electron tube 3A to ground, and operating potential is applied to the plate via a load resistor 59 connected to the B plus supply terminal 65 via a lead 66. The electron tube 3A amplifies the organ signal and applies it through a coupling capacitor 60 to the recording head 18.

Assuming that a switch 83 is closed, and that the oscillator 73 is in operation, erase current passes through the erase head 15, and bias current passes through record head 18. As the recording tape 14 is drawn in the direction indicated by the arrows out of the tape magazine 9, over the pulley 16, past the heads 15, 18, 19, 20 and 21, and back to the magazine, the erase head 15 removes any magnetic signal which may be already on the tape. The demagnetized tape then passes the record head 18 where the signal from the organ is recorded upon the tape. The tape then passes the pickup head 19, where the recorded organ signal on the tape is picked up and applied via a lead 37 to the grid of an electron tube 2, which may comprise a high gain amplifier pentode such as tube type 6AU6. The tape next moves past the pickup head 20, and here the signal is picked up again, and assuming that a switch 33 is open, the signal passes through the winding of the pickup head 19 to the grid of pentode 2 via a lead 37. As the tape moves past the pickup head 21, again the signal is picked up and passed through the windings of the heads 20 and 19 in series, to the grid of the electron tube 2. Thus, the organ signal appears three times in rapid succession at the grid of the electron tube 2. The actual time elapsed between each signal pickup is dependent upon the relative spacing between the recording head 18 and the pickup heads 19, and 21, and also upon the velocity of movement of the magnetic tape as it moves past the heads.

A cathode resistor 38 is connected between the cathode of electron tube 2 and ground, and a plate load resistor 39 is connected to the B plus supply terminal 65 via the lea-d 66. A screen resistor 40 is also connected to the B plus terminal 65 via the lead 66. The screen of the tube 2 is bypassed to ground by means of a capacitor 41 and a plate coupling capacitor 42 carries the amplified signal from the plate of tube 2 to the grid of an electron tube 3B, which may comprise the second triode section of the tube type 12AU7, which also includes the electron tube 3A as described above. A cathode resistor 44 returns the cathode of the tube 33 to ground and operating voltage is applied to the plate via a plate ioad resistor 45 from the B plus supply terminal 65 via the lead 66. The electron tube 38 amplifies the signal and the amplified signal passes through a plate coupling capacitor 46. A part of the amplified signal is applied, via a resistor 47 and a resistor in series to the grid of the electron tube 3A, and another part of the amplified signal is applied to a potentiometer 80 via a resistor 54. The potentiometer 80 serves as a gain control for an amplifier 78 which drives a speaker 79. Thus, the signal from the tone generator 82 first is reproduced by the organ speaker 77 and then by the speaker 79, slightly delayed in time, and with other characteristics described below.

That portion of the signal from the electron tube 3B which reaches the grid of the electron tube 3A is amplificd again and recorded on the magnetic tape again according to the cycle of events described above. A recurrent loop is thus established, and the signal continues to travel around the loop with decreasing amplitude at each new recording. The amount of this amplitude decrease is controlled by the value of the resistance of a variable resistor 49 which is connected as a shunting arm between the junction of the resistors 47 and 50 and ground. When the resistor 49 is adjusted to have zero resistance, the signal from the electron tube 3B is not passed to the grid of the electron tube 3A, and the signal is not transmitted around the loop. However, the signal from the tone generator 82 reaching the grid of the electron tube 3A is not impeded and likewise the signal reaching the amplifier 78 is not impeded. This is due to the relatively high resistance values of resistors 47 and 50, which serve as isolation resistors. Thus, even when the resistor 49 is set to zero, the direct organ signal is reproduced by the speaker 77 and the recorded and delayed organ signal is reproduced by the speaker 79. The resistor 49 has a maximum critical resistance value at which the signal appearing at the grid of the electron tube 3A from the reentrant loop is just equal to the signal applied to that same point from the bone generator 82. With an adjustment of the resistor 49 at the maximum critical resistance value, the gain in the reentrant loop is exactly equal to one, and the signal, once introduced to the loop, continues indefinitely. To overcome this undesirable condition, the reentrant loop should always be operated with a gain of less than one so that each succeeding transit of the signal around the reentrant loop produces a lower voltage at the grid of the electron tube 3A than the last, with the result that the signal gradually dies away.

The rate at which the signal dies away depends upon the gain in the reentrant loop, and with low gain the signal will die away faster than when the gain is close to one. A capacitor 48, which is connected in parallel with the variable resistor 49, reduces the gain within the reentrant loop for high frequencies, so that high frequencies will die away faster than the low frequencies. Because of the three successive pickup heads 19, 20 and 21, attenuation does not start until the signal from the last head, namely 21, has been picked up and amplified. Thus it will be seen that there are two factors which control the 6 time of signal die away, i.e. the rate of attenuation. These factors are the spacing of the pickup heads along the path of the magnetic tape relative to the recording head, and the gain of the reentrant loop, as controlled by the re sistor 49.

In order to simulate as nearly as possible natural reverberation, the strength of the signals from the three successive pickup heads should not be equally loud, but should diminish somewhat, so that the signal from the head 20 is less than that from the head 19, and the signal from the head 21 is less than that from the head 20. For this reason a resistor 36 is connected across the winding of the head 21, and a variable resistor 34 is connected serially with a capacitor 32 to the junction of the heads 19 and 20, so that in effect it is shunting both heads 20 and 21. Since the three pickup heads 19-21 are connected in series, the total average voltage appearing at the grid of the electron tube 2 from the three picked up signals will be higher than the signal from pickup head 19 alone. The maximum resistance value of the resistor 34 is chosen so that the individual signals from heads 20 or 21 are slightly lower than the signal from head 19. The capacitor 32 provides bass compensation by presenting a lower impedance to the passage of high frequency signals than to low frequency signals. When the value of the resistor 34 is reduced it lowers the signal voltage from heads 20 and 21, and at the same time it lowers the total average signal voltage appearing at the grid of pentode 2. Thus, variable resistor 34 serves as a very eifective means for controlling the reverberation, or signal die away time, in the reentrant loop, from several seconds down to a small fraction of a second. This feature permits the organist to make rapid changes in reverberation efiect even while playing.

Since the slow die away of percussive instruments, such as the piano for example, is similar to the die away of reverberation, an effect of percussive sustain may be achieved by means of the present invention. To enhance this effect a foot operated sustaining pedal (not shown) may be employed to control the opening and closing of a normally open switch 33. This switch when closed, operates to ground lead 35, thereby short circuiting the variable resistor 34. This causes the reverberation die away time to be a minimum during the time the switch is closed. When the switch is opened the die away time is restored to that determined by the value of the resistor 34. Thus the player can by opening and closing the switch 33 with the sustaining pedal, produce an effect similar to that obtained with the sustaining pedal of a piano.

In a practical instrument the variable resistor 49 adjustment need not normally be accessible to the player and may be adjusted as follows: With the switch 33 open, and the variable resistor 34 advanced to the point of maximum gain, the variable resistor 49 is adjusted until the gain of the recntrant loop is slightly less than one. This is accomplished by advancing the variable resistor 49 until an organ tone, when briefly played, sounds continuously after the key is released. The control is then turned back slightly until the tone stops. This is the setting for maximum useful gain and reverberation.

The output resistor 54 is shunted by a capacitor 55, and a low pass filter comprised of the resistors 51 and 52, and a capacitor 53 to compensate for deficiencies in the frequency response characteristics of the recording system. The input resistor 57 is shunted by a capacitor 56 to acoomplish the same purpose.

The following table of circuit component values for the arrangement of FIG. 4 is given by way of example on y:

Capacitor 32 rnicrofarads 2 Capacitor 41 do .05 Capacitor 42 do .01 Capacitor 46 do .02 Capacitors 48, 53 do .005

Capacitors 55, 56, 68, 69 microfarads .0001 Capacitor 60 do .1 Capacitor 61 do .001 Capacitor 62 do .0005 Capacitor 67 -do .0015 Resistor 34 ohms 10,000 Resistor 36 do- 4,700 Resistor 38 do 3,300 Resistors 39, 47, 50, 51, 52, 57, 80, 86 -do 500,000 Resistors 40, 43, 54 megohm 1 Resistors 44, 58 ohms 2,200 Resistors 45, 49 do 100,000 Resistor 59 do 56,000 Resistors 70, 72 do 200,000 Resistor 71 do 1,500 Windings 63, 64 millihenries 5 In the installation of an organ in accordance with the invention, the speakers 77 and 79 should be spatially separated. The spacing is not critical, but best results are obtained if they are located in such a way that the listener is more or less between the speakers. In this way the acoustic signal from the speaker 77 will tend to be louder in one ear of the listener, and the signal from the speaker 79 will tend to be louder in the other ear of the listener. The loudness of the reverberant tones coming from speaker 79 is adjusted by the player by means of the volume control 80 for the musical effect desired. This is not a fixed control, and may be frequently changed by the player, depending upon what type of music he is playing. As an example, in playing church music, this control will usually be adjusted so that the reverberant tones from the speaker 79 are as loud as the direct tones coming from the speaker 77. For faster moving popular music, the player may wish to reduce the loudness of the reverberant tones, and at the same time shorten the length of reverberation by reducing the resistance of the variable resistor 34. Controls for these two variable resistors may be placed upon the control panel of the organ where they are readily accessible to the player.

Referring now to FIG. 10, the generation of ensemble effects in accordance with the invention is explained as follows: The recording head 18 and the first two pickup heads 19 and 20 of FIG. 4 are shown. The magnetic gap of the head 19 is indicated as 19A and the gap of the head 20 is indicated as 20A. The moving magnetic tape 14 is passing the recording head and the two pickup heads, in the direction indicated by the arrow. It is assumed that head 18 is continuously recording upon the magnetic tape a steady tone of constant frequency. The actual physical spacing between the magnetic gaps of heads 19 and 20 is indicated as distance D. The windings of heads 19 and 20 are connected serially, and voltages of like polarity which are induced in them will be additive, while voltages of opposite polarity will tend to cancel. Assume that the signal frequency being recorded upon the tape is 500 cycles per second, and that the tape is moving at exactly five inches per second. If distance D is exactly one inch, there will be recorded upon the tape in the distance D exactly one hundred cycles. Each cycle will thus occupy a space of .010 inch, and this is the wavelength of the recorded signal. Under these conditions the vector sum of the voltages being induced in the pickup heads 19 and 20 will be approximately double the voltage of either head taken separately, because the voltages are in phase. Now suppose the tape velocity changes slightly, so that instead of there being exactly one hundred cycles recorded within the distance D, there are now ninety-nine and one-half cycles in that space. The result of this will be that the voltages induced in pickup heads 19 and 20 will be out of phase and will tend to cancel one another. Suppose that the tape velocity continues to change so that there are now ninety-nine and one-quarter cycles recorded in the distance D, and then later ninety-nine and threequarters cycles recorded in the distance D. It will be seen that the vector sum of the voltages will be continuously changing so long as the tape velocity continues to change. It should be noted that these are not discrete changes in phase, but continuous changes, accompanied by actual vector rotation. This fact is readily observable by the use of Lissajous figures on an oscilloscope. This is important because in the ensemble effect observed with the organ or symphony orchestra, and which is produced herein artificially, the continuously changing vector relationships of the sounds in the listeners cars is a very pleasing musical effect. In musical language these vector changes are called beats.

At this point the distinction between the ensemble effect caused by phase shifting and the reverberation effect resulting from time delay in reproduction of the signal should be fully appreciated. Both effects result primarily from the velocity of the tape on which the signal is recorded. However, reverberation effects result from the relatively large time delay between the recording of the signal at the recording head and its subsequent reproduction by the pickup heads 19 and 20, which delay approximates the time interval between particular sound being heard by a listener, first, directly from the musical instrument and then later being returned from a reflecting surface in echo fashion; whereas the ensemble effect depends upon no fixed delay but only upon slight variations in tape velocity, in the above example about one percent, which produce the slight phase variations. The delay between recording and pickup, which produces the reverberation effect, may be considered for practical purposes as a fixed time interval. There will be slight variations in this delay time interval due to the slight variations in tape velocity but the mean time between recording and pickup remains substantially constant. On the other hand, the phase shifting of the signal for ensemble effect involves relatively small time variations compared to the large fixed mean delay for producing reverberation elfects; the small time factor here is a variation which is continuous and random about a zero point and relates to the spacing on the tape between individual cycles of the signal. Thus, it may be seen that the two effects even though accomplished by the same means are essentially completely different in character, one depending upon a large fixed mean time delay and the other upon relatively small variations in time which are continuous and random about a fixed point.

The changing phase relationship just described was that which occurred when the frequency was 500 cycles. A similar effect will take place at other frequencies, since it is not the number of cycles recorded on the tape within the distance D which is important, but only the instantaneous phase relationship of the signals which are being simultaneously picked up by the two heads. In the system of the present invention, small random changes in tape velocity are taking place continuously, as will later be explained more fully. These changes cause small differences in the wavelengths of all the signals as recorded upon the magnetic tape. Any given instantaneous displacement in tape velocity will cause less phase difference at low frequencies than at high frequencies because the wavelengths are longer at the low frequencies and a greater displacement is required to produce a given phase difference. This is very desirable, since this is exactly what happens in the tones from an organ or an orchestra, where the beats occurring in the low notes are slower than those occurring in the treble notes. An equally important result is that the actual phase difference will be different for each musical note, and this tends to avoid the monotony which would occur if any fixed repetitive pattern of phase differences or beats should occur as would be the case in a conventional tape recorder mechanism having repetitive wow and flutter. A definite pattern of beats is easily detectable and is unmusical and undesirable. Asa further aid in avoiding any detectable beat pattern, three pickup heads may be used, as is shown in'FlG. 4 and FIG. 1.

The principle of producing beats by phase differences between signals in two pickup heads as described above in connection with FIG. 10, will operate with any two pickup heads, such as heads 20 and 21, or heads 19 and 21 in FIG. 4. Thus while beats are generated between heads 19 and 20 as described'above, other beats are simultaneously generated between heads 20 and 21, and also between heads 19 and 21. The combined pattern of these three sources of beats is extremely complex, and not at all repetitive due to the fact that there is no repetitive pattern of wow and flutter.

FIGS. 1, 2 and 3 show respectively the plan view, the side view, and the bottom view of the physical arrangement of one actual system in accordance with the invention. In FIG. 1, a metal chassis plate 1 supports all the tape recording mechanism and associated electronic circuit components, including the electron tubes 2, 3- and 4 of FIG. 4. A rectifier tube 6 and power transformer 7 form part of the B plus supply circuit, not shown but indicated in FIG. 4 as a terminal 65. The transformer is disposed between the tubes 4 and 6. In FIG. 1 the tape 14 is drawn from the tape magazine 9 by means of a capstan 10, with the pressure rollers 11 and 12 pressing the tape into engagement with the capstan. The tape moves successively past a tape guide 13, the erase head 15, a pulley 16, a tape guide 17, the record head 18, the first pickup head 19, the second pickup head 20, the third pickup head 21, a tape guide '22, the capstan 10 and pressure roller 11, and back to the magazine 9. One important feature of this arrangement is that the tape passes the capstan twice, withpressure rollers 11 and 12 holding the tape firmly against the capstan. Thus a closed loop of tape is formed with the capstan controlling the velocity of the tape moving into as well as out of the closed loop, so that a uniform tape velocity is provided in an inexpensive structure. One of the major problems in designing any tape recording device is to obtain a structure which provides constant tape velocity. This of course is necessary in order to reduce wow and flutter to a minimum.

In conventional tape recording equipment, where the tape is transported from one storage reel to another, and where each reel maintains a constant tension on the tape, there is a relatively constant load on the tape and driving capstan. In contrast, where a tape storage magazine is employed, the problem is somewhat different due to the varying load which a tape magazine presents to the tape transporting mechanism. At the present state of the art, tape magazines generally present a varying load due to the sliding of the turns of tape against each other, and the friction introduced thereby. The motor 8 is arranged to drive the capstan, as well as the tape magazine 9, and details of this arrangement are shown in FIGS. 2 and 3.

FIG. 2 is a side elevation of the apparatus of FIG. 1, showing details of the tape transporting mechanism. Certain items, such as the tubes and power transformer have been omitted from FIG. 2 for the sake of clarity. FIG. 3 is a bottom view of the same assembly, and like characters are used to indicate like parts in the three figures. The router 8 is resiliently mounted upon the chassis plate 1, and on the motor shaft is mounted a pulley 31 having two grooves and carrying two drive belts 30. These belts turn a large pulley 29, which also has two grooves. The pulley 29 is mounted upon a shaft 24, upon which the capstan 10 is mounted. The shaft 24 maybe supported by a first bearing 24A where it passes through the chassis, and by a second bearing (not shown) at the end opposite the pulley 29. A small pulley 25 is also mounted upon the shaft 24, which by means of a belt 26, drives the large pulley 27. The pulley 27 is mounted upon a shaft 28 which passes through the chassis panel 1, and

provides the power to drive the tape magazine 9. The shaft 28 may be supported by an upper bearing 28A Where it passes through the panel, and by a lower bearing (not shown).

In the usual tape recorder structure, it is customary to construct the capstan surface of steel, and the pressure roller which presses the tape against the capstan of rubber or some similar material which has a non-slip surface, so that slipping is prevented. This is very important since the slightest slip will cause irregularity in tape travel. The pressure of the roller against the capstan is, for the same reason made quite heavy. This necessitates some kind of mechanical linkage to disengage the pressure roller from the capstan when the equipment is not in use, in order to prevent the formation of flat spots in the rubber surface of the pressure roller. In order to eliminate the expense of such a linkage and at the same time to increase the friction between the capstan and the pressure roller, the present structure employs a capstan with a rubber surface, which is in contact at all times with the pressure rollers. This permits the use of much less pressure between the capstan and the rollers, and eliminates the possibility of flat spots, since there is no hard surface pressing into either rubber surface. This arrangement more than doubles the friction area against the tape and reduces the possibility of tape slippage. As shown in FIG. 2, the capstan 10 is of greater diameter than the capstan shaft 24 and may comprise a section of thick walled rubber tubing pressed onto the shaft 24.

It should be understood that the present disclosure endeavors, among its other objects, to convert to an advantage, one of the commonest limitations of the usual tape recorder structures, namely irregularity in the velocity of tape movement. The effects variously known as wow and flutter in tape recorder design, and which are highly undesirable therein, are used to advantage in the system of the invention to enhance the ensemble ellect. Perhaps the commonest source of flutter is that which is due to the eccentricity of the capstan, and is evidenced as a moderately fast frequency modulation, the frequency depending upon the revolutions per second of the capstan. In organ music a frequency modulation of the tones at a frequency of from six to seven cycles per second is known as vibrato, and is frequently used to artistic advantage. Therefore, in accordance with the invention, the ratio of the motor drive pulley 31 and the capstan pulley 29 is selected so that the capstan rotation will lie between six and seven revolutions per second. With this arrangement, any flutter due to the capstan rotation will appear as vibrato and will add to, rather than detract from, the ensemble effect desired. Unless a heavy vibrato is desired, the capstan should not be made intentionally eccentric.

Probably the commonest source of wow is that which is due to the rotation of the pressure roller which holds the moving tape'against the capstan. The present invention endeavors also to utilize this normally undesirable effect to advantage. Wow, like flutter, is a periodic change in frequency of the tones being reproduced, but occurs at a much lower rate per second, and to the listener it produces an unpleasant musical effect which can best be described as a periodic out of tune-mess. If the amount of frequency shift is not enough to be considered out of tune, still the effect is unpleasant, due to the fact that it is repetitive and monotonous.

In accordance with the invention, certain types of wow may be used to advantage. In an orchestra or pipe organ, the frequency difference between instruments or pipes sounding the same musical note will usually fall between two cycles or beats per second to a fraction of a cycle per second. If the beat is much over two pets-second the tones begin to sound out of tune, at least in the octaves near middle C, where the ear is quite sensitive to pitch difierences. As previously described, changes in tape velocity in this invention produce in effect musical beats due to vector additions and cancellations in the pickup heads. Small changes in tape velocity, therefore, which occur at a rate slower than approximately two cycles per second, will enhance the ensemble by the production of musical beats such as are heard in an orchestra or pipe organ. In the present structure there are a number of factors which contribute to the wow, and which can therefore be employed to enhance the ensemble efiect desired. These factors are:

(1) Motor speed (2) Rotation speeds of pressure rollers (3) Rotation speed of pulley 16 (4) Rotation speeds of belts Rotation speeds of the pulleys 2S and 27 do not contribute much because the load presented by the tape magazine is light. The load on the tape which is presented by the tape magazine itself is insulated from the enclosed tape loop, by means of the pressure roller 12 and the capstan. With the line voltage stability normally encountered, the constancy of motor speed rotation produces no noticeable wow. However, a controlled amount of wow may be introduced intentionally by periodically introducing a small value of resistance in series with the motor winding and the line. Thus, in FIG. 2 a simple switch 8A automatically operated, can be used to periodically short circuit a series resistor SE at intervals of approximately once per second. The resistance can be made variable, so that the degree of the effect is under control of the player.

Since rubber tired pressure rollers have a tendency to cause wow, even when carefully made, it is desirable in the present structure, to make their contribution as nonperiodic as possible. Suppose that pressure rollers 11 and 12 each contribute a small amount of wow, which when taken alone is within the acceptable limit of wow. But suppose that both rollers are the same diameter and are therefore turning at exactly the same speed, for ex ample, one revolution per second. The wow will now be approximately doubled in the worst case, and it will become noticeable and monotonous, due to its frequent repetition. But suppose that one roller is ten percent larger in diameter than the other. The wow contributed by the two rollers taken together will coincide approximately every tenth revolution. If one revolution takes approximately one second, then the pattern will be repeated not oftener than once in ten seconds. This is so long a period that the car will not identify it as a monotonous pattern. The pulley 16 should have a diameter different from the diameters of the rollers 11 and 12 for the same reason.

The pulley 16, and the rollers 11 and 12 are all mounted upon free turning bearings 23. The pulley 16 serves a double purpose, and should be made of material such as brass, so that it will have a relatively high mass. It serves as a mechanical low pass filter, so as to smooth out irregularities in the movement of the magnetic tape, and also provides a large radius for the turning of the tape as as it begins its return trip past the heads to the capstan. Note that there are no small radii anywhere in the enclosed tape loop from the roller 12 to the roller 11, which contributes to the smooth movement of the tape. The tape which is stored in the tape magazine, since it is a continuous loop, must of course have a splice. Since the splice is stiffer than the rest of the tape, it will cause a momentary frequency shift if it passes a small radius anywhere in the enclosed tape loop. When the pulley 16 is at least 1% inch in diameter, the passage of the splice is almost imperceptible, even when a steady tone is being played.

Another important source of wow in this structure is the drive belt 30. A soft flexible belt should be used here such as rubber, but often the belt rotation itself will introduce a small amount of wow which occurs with every rotation of the belt. Due to slight irregularities in belts, the rates of rotation of two similar belts will seldom be the same. Therefore, in one form of the invention, two similar belts 30 are used, running on two double pulleys 31 and 29. The wow pattern is altered by the use of two belts, in a manner similar to that described above in connection with the pressure rollers. The overall wow pattern of the pressure rollers, the pulley 16, and the drive belts 30 is so complex that it cannot be identified as a repetitive pattern, thus removing any wow monotony from that source. In considering the practical operation of a system in accordance with the invention, another factor regarding the wow must be considered. As is well known, wow as it is normally known in phonograph or tape reproduction, is a slight rising and falling in the pitch of any tone being reproduced. At any instant therefore, the actual pitch of a tone may be either fiat or sharp to the true or average pitch of the tone. The same of course is true in this device, but it must be remembered that the listener does not normally hear the tone from a single reproduction, but from multiple reproductions which are being heard simultaneously. Thus, if at any instant one reproduction is sharp, another may be on average pitch, and another may be flat to the average pitch. Musically, this is precisely what is happening when several instruments or organ pipes sound the same note simultaneously. Therefore, it will be seen that random wow contributes greatly, and in a number of ways, to the ensemble effect generated with the present invention.

The importance of the spacing between the heads along the path of the magnetic tape has previously been mentioned. A more detailed discussion of various pertinent dimensions follows. In one structure the following dimensions were used. The diameter of the capstan 10 was .318 inch and the circumference was one inch. The rate of revolution of the capstan was six per second. The tape travel, therefore, equalled six inches per second. In order to make the first signal pickup occur as soon as possible after the onset of the organ tone, the first pickup head 19 may be placed as close as possible to the record head 18, in this case inch. The second pickup head 20 should be placed so that its distance from the record head is not an even multiple of the distance between the record head and the first pickup head. This is done so that successive recordings picked up by the first and second pickup heads do not come at the same instant, since this would produce a monotonous repetitive pattern, which is not characteristic of natural reverberation. For the same reason the distance from the record head to the third pickup head 21 is not an even multiple of the spacing to either of the first two pickup heads. The distance chosen for the second head may be 2% inches and for the third head 4 inches.

The location of the erase head 15 is not critical, and is approximately as shown in FIG. 1. The pulley 16 should be placed as close as possible to record head 18 as shown. Similarly, the last pickup head 21 should be as close as possible to capstan 10 and pressure roller 11. Suitable diameters for the pressure rollers are 1% inches for roller 12, 1% inches for roller 11, and 1% inches for pulley 16.

It has been mentioned that the rotation rate of the capstan is selected to lie between six and seven revolutions per second, so that any unintended variation in the capstan rate would sound like vibrato instead of wow. It is also possible to equip the capstan shaft with some kind of variable load to artifically introduce vibrato, by periodically changing the rate of shaft revolution. This may be done in any convenient way that causes the load to change during the rotation of the shaft. It may be done mechanically, or as shown in FIG. 2, by means of a magnetic brake 24B which loads the shaft 24. By applying suitable signals to the brake 2413, the amount of loading may be changed in degree, or turned off at will.

It is also possible to obtain an effect similar to vibrato by placing the pickup heads at such distances from the record head that the successive reiterative recordings and re-recordings of the signal will occur at vibrato periodicity, for example six per second. In this case the second and third pickup heads should be spaced at distances which are exact multiples of the distance from the record head to the first pickup head. For example, the four heads can be spaced one inch apart. This arrangernent also permits the player to obtain a musical effect resembling that obtained from a marimba, by playing successive, rolling, staccato chords on the organ. The notes thus played are repeated six times per second during the period of die away, and resemble the percussive notes of the marimba or other similar percussive instrument. The fact that this arrangement requires equal spacing of the heads, while that best suited for the ensemble elfeot requires unequal spacing of the heads, does not mean that the two features cannot be used in the same structure. By providing multiple heads, some of which are evenly spaced, and some of which are unevenly spaced, either of the desired elfects may be used, by means of selection switches which short circuit the undesired heads.

Another desirable feature of the system of the invention is that it can be used effectively as a self-teaching device to assist a player in improving his playing technique. When one is playing the organ, particularly a beginner, almost complete attention is required merely to play the notes correctly. The player cannot devote much of his attention to critically listening to the musical elfects which he is producing. If, therefore, he is able to devote his entire attention to listening to a piece which he has just played, he can by correcting the mistakes which he hears, markedly improve his own playing. The present structure permits the player to do that.

In the system of the invention illustrated in FIGS. 1 and 4, the magnetic tape is stored in a tape magazine 9. While for the purposes of the invention thus far described, a very small continuous tape loop would suffice, there are two principal reasons for using a much longer tape loop, with the excess tape stored within a magazine during operation. First, the matter of wear makes it undesirable to use a short tape loop. Since the tape mechanism is in operation continuously while the organ is being played, the tape should be long enough so that it does not have to be replaced too frequently due to wear. Second, in order to utilize the self-teaching feature, enough tape must be stored in the magazine so that one or two musical selections can be played before the tape begins to repeat. Experience indicates that if from two to three minutes of tape is provided, this will sufiice. It tends to defeat the purpose of the system as a self-teacher if the player has to wait as much as four or five minutes to hear what he has played. Two and a half minutes seems to be about the optimum time. With a tape speed of six inches per second, one minutes playing requires thirty feet, and a total of seventy-five feet of tape is therefore employed.

To use the device as a self-teacher, the organ is played for a period of approximately two and one-half minutes with switch 83 in FIG. 4 in the closed position. At the end of this period the switch is opened. This stops the bias oscillator 73, and removes erase voltage from head 15, and bias voltage from head 18. The signals which are stored on the tape will now be picked up by heads 19, 20 and 21 and reproduced in speaker 79. No sound will come from speaker 77, but the tones coming from speaker 79 will have ensemble and reverberation, although the stereophonic reproduction will be lacking. The equipment will play the two and one-half minute recording over and over until the switch 83 is again turned to the ON position, and the equipment is thus made ready for another recording.

It has been stressed that the stereophonic reproduction of the ensemble is an important feature of this invention, because of the seeming movement of the tones in the ears of the listener. The term stereophonic as here used, includes simulated three dimensional auditory perspective effects as well as true spatially discriminatory recording and reproduction. A number of physical arrangements of the amplifiers and speakers which may be employed to achieve this effect are shown in FIGS. 4, 5, 6, 7, 8 and 9. FIG. 5 illustrates one arrangement wherein both amplifiers 76 and 78, and their associated speakers 77 and 79 are installed in the organ console, with one speaker mounted in the front wall of the console and the other speaker installed in the back Wall. FIG. 6 is similar to FIG. 5 excepting that the two speakers are mounted in opposite end walls of the organ console. The latter arrangement provides somewhat better spatial separation of the tones. In FIG. 7 the ensemble and reverberation amplifier 78 and its speaker 79 have been installed separately in a tone cabinet 93, while the organ amplifier 76 and speaker 77 are in the console 81. This is a preferred arrangement, because the tone cabinet and organ can be placed on opposite sides of the listening area for maximum stereophonic effect. Gain control 80 serves the same function as in FIG. 4.

In FIG. 8, organ amplifier 76 and its speaker 77 have been installed in a separate tone cabinet 84, with the amplifier 78 and speaker 79 in another tone cabinet 93. FIG. 9 shows both amplifiers and both speakers mounted in a single stereo cabinet, with the speakers mounted in opposite ends of the cabinet to obtain spatial separation. It might be thought that the arrangements shown in FIGS. 8 and 9 are better than those in which the organ amplifier and speaker are mounted in the organ, but such is not necessarily the case, although it is probable that better bass reproduction would result therefrom. Actually the best arrangements are those in FIGS. 5, 6 and 7, because here the organ speaker 77 is mounted in the organ console. This gives rise to a pleasing phenomena which is explained as follows: The vibrations from the speaker, especially from the bass notes of the organ vibrate the console and the keyboard to such an extent that the player can feel the vibrations in his hands, as he plays. This, in some way, enhances the feeling of bigness and grandeur imparted to the organ tones which is probably due to a psychological reaction related to the fact that we associate physical vibration sensations with the music from pipe organs in large reverberant enclosures. Therefore, the best results are achieved with the system of the invention when the organ speaker 77 is installed in the organ console. Speaker 79 may be mounted either in the console or separately, as shown, although better spatial effect is probably obtained when it is mounted separately in a tone cabinet.

FIG. II shows a simple arrangement, wherein a single amplifier 76 and single speaker 77 are used to reproduce both the direct organ signal, and the ensemble and reverberation signal. FIG. 11 is to be used in connection with FIG. 4, and terminal A of FIG. 11 corresponds to terminal A of FIG. 4. Likewise, terminal B in FIG. 11 corresponds to terminal B in FIG. 4, all the equipment and circuit above terminals A and B in FIG. 4 having been omitted from FIG. 11. Variable resistance control 86 in FIG. 11 makes it possible to adjust the relative amounts of direct organ signal, and ensemble and reverberation signal, transmitted to the amplifier 76. Its musical function is similar therefore to that of control 80 in FIG. 4. While the arrangement in FIG. 11 does impart reverberation, and some ensemble to the organ tones, the spatial feeling of stereophonic reproductoin is lacking.

In the system disclosed herein the ensemble and reverberation effects are obtained through use of magnetic tape recording techniques, but it will be appreciated that any type of recorder may be used to obtain similar effects, so long as there is a moving recording medium such as, for example, a disc having a wax or rubber surface, so long as there are discrete pickup points, either magnetic, electrostatic, or mechanical.

Although a number of specific arrangements for practicing the invention have been described above, it is not intended that the invention be limited thereto. Accordingly, any and all modifications, variations or equivalent arrangements falling within the scope of the annexed claims should be considered to be a part of the invention.

What is claimed is:

1. In combination with an electronic organ having a tone generator for providing first electrical signals corresponding to musical notes, delaying means coupled to the tone generator and arranged to provide successively delayed duplications of the first electrical signals, at successively later fixed mean times, said delaying means including means for introducing a continuous superimposed phase change into each of the duplications for producing essentially random phase shifts of the duplications with respect to the first electrical signal, and means combining the duplications into a second electrical signal, whereby the simultaneous reproduction of said first and second electrical signals creates an effect of musical ensemble and reverberation.

2. In combination with an electronic organ having a tone generator for providing first electrical signals corresponding to musical notes, means for creating reverberation and ensemble effects coupled to the tone generator, said reverberation and ensemble means producing second electrical signals representative of the first electrical sig nals and each having a continuous random oscillatory phase change efiect, said reverberation and ensemble means also including circuits for successively repeating the second electrical signals at selected unlike intervals with further continuous random phase change effects, and means simultaneously reproducing the first and second electrical signals to produce ensemble and reverberation efiects.

3. A controllable musical device responsive to musical tones for creating ensemble and reverberation efiects including the combination of a cyclic recording medium, means for moving the recording medium with random variations from a nominal rate, the random variations constituting continuous phase changes in an electrical signal recorded thereon, a recording device associated with the recording medium and responsive to the musical tones for recording the tones on the medium with first continuous phase variations, a number of reproducing devices positioned along the path of the recording medium with relatively unequal spacings with respect to each other and the recording medium, each of the reproducing devices reproducing signals recorded on the medium with second continuous phase variations, the reproduced signals being essentially random phase relative to each other, means coupled to each of the reproducing members for combining the signals reproduced thereby into a single combined signal utilizing relatively unequal contributions from the reproducing members, a feedback circuit coupled between the combining means and the recording member and attenuation means included in the feedback circuit for controlling the rate of attenuation of the combined signal.

4. Apparatus for introducing controllable reverberatory effects in the musical tones provided by a musical device, including the combination of a moving recording medium traveling along a predetermined path, means for producing a minor random variation in the rate of travel of the moving recording medium, thus to provide a continuous variation in phase a member coupled to the musical device for recording the tones therefrom on the recording medium, a plurality of reproducing members each of which is positioned along the path of the recording medium at a successively further point from the recording member along the path of the recording medium and each reproducing signals in fixed delay and random phase relation, an electrical circuit coupling the reproducing members in a series relation, the electrical circuit including attenuation elements for deriving unequal contributions from the signals from the individual reproducing members, said electrical circuit also including means for attenuating high frequency signals relative to low frequency signals, and an adjustable attenuator coupling the series of reproducing members to the recording member to establish a reentrant loop in which the attenuator provides a controlled amount of gain within the reentrant loop,

5. A stereophonic musical device including in combination a unit having a tone generator and providing a combined electrical signal output representing musical notes, at least two spaced speakers, a first signal channel coupling the combined output from the musical unit to at least one of the speakers as a first electrical signal, a second signal channel responsive to the combined output from the musical unit and providing therefrom to at least another of the speakers a second electrical signal, said second signal channel including means for introducing a continuously variable phase shift of the signals passing therethrough having at least one substantially fixed delay interval relative to the first electrical signal whereby the combined reproduction of the electrical signal by the speakers produces the effect of musical ensemble and reverberation.

6. A stercophonic musical system including a tone generator for providing an initial output signal, at least two spaced speakers, one of which is responsive to the output signal from the tone generator, and a reentrant loop circuit including recording and reproducing means coupling the output of the tone generator to at least one other of the speakers, the circuit including means for continually varying the recording and reproducing rates across a range of phase values, the reproducing means providing multiple signals at fixed delay intervals which are subject to the variable phase shifts control means coupled to maintain the recording medium continuously with the fixed delays being selected to correspond to reverberation times and with the phase shift introducing ensemble effects when the output and recombined signals are reproduced simultaneously by the speakers.

7. Apparatus for providing a controllable reverberation effect in the musical tones provided from an electronic musical system, the apparatus including the combination of a controllably movable recording medium control means coupled to maintain the recording medium continuously, moving at a varying rate, the variation in said rate being random, a recording member responsive to the electronic musical system for recording signals therefrom on the recording medium, a number of repr0 ducing members spaced along the path of movement of the recording medium at successively further points from the recording member, means coupled to each of the reproducing members provide successively smaller signals, the spacings between the reproducing members being selected to provide desired delay times, a circuit connecting the reproducing members in series and including a controllable attenuator shunting the series connection at a selected point to provide one control of the reverberation characteristics, and a controllable attenuation cir cuit coupling the series connected reproducing members to the recording member, the controllable attenuation circuit adjusting the loop gain to be less than unity and providing a second control of the reverberation characteristics.

8. Apparatus for providing a supplementary reverberation and ensemble elfect in the outputs provided by an electronic musical system, the apparatus including the combination of a driven recording medium, a continuousdrive mechanism for the recording medium providing both a minor random variation and a cyclic variation characteristic of a frequency approximating that of a vibrato, a recording member responsive to outputs of the electronic musical system for recording signals on the recording medium, and a reproducing mechanism including a series of spaced reproducing elements positioned along the recording medium for providing a second output having successively delayed components, each of which continuously changes in accordance with the random and vibrato variations of the drive mechanism.

9. Apparatus for introducing ensemble effects into musical tones provided by an associated system, including the combination of a recording and reproducing mechanism responsive to musical tones, the mechanism including a recording means, a record member and a reproducing means, the recording and reproducing means being positioned to provide at least one duplication of the musical tones at a substantially fixed delay interval, and a drive mechanism coupled to control the record member at a variable rate for introducing an essentially random phase change in the reproduced tones, said drive mechanism including pressure members engaging the record member which are of like characteristics but not identically matched, a rotary capstan disposed in operative association with the pressure members, and drive means including a pair of drive belts coupled to the capstan and which are of like characteristics but not identically matched.

10. In an electronic organ in which electrical signals are generated corresponding to musical notes, means for creating artificial reverberation and ensemble efiects including the combination of a first signal channel for directly reproducing the electrical signals generated by the organ, a variable phase changing and delay device, the device including a movable record means, and physically spaced recording and reproducing means associated with the record means, and means for moving the record means at a continuously randomly varying rate, for producing successively delayed electrical signals of continuously varying phase corresponding to the electrical signals generated by the organ, and a second signal channel coupled to the variable phase and delay device for reproducing the electrical signals of continuously varying phase whereby upon simultaneous reproduction of the phase varying signals along with the original electrical signals the effect of ensemble and reverberation is achieved.

11. In an electronic organ in which electrical signals are generated representing musical notes, means for creating artificial ensemble and reverberation effects including the combination of a first signal channel for reproducing directly electrical signals produced by the organ, a continuously movable recording medium, means for transporting the recording medium with velocities which continuously vary over a phase responsive range from a predetermined nominal velocity, a recording means positioned along the path of travel of the recording means and recording electrical signals derived from the organ with continuously varying phase changes, a plurality of pickup means positioned along the path of travel of the recording medium trailing the recording means, each of said pickup means generating an electrical signal representing the recorded signals on the recording means, said pickup means being spaced apart whereby the recorded signals passing adjacent thereto produce successively in each of the pickup means an electrical signal which is delayed with respect to the electrical signal applied to the recording means with variations in the velocity of transport of the recording medium producing additional and randomly varying phase changes in the electrical signals produced by each of the pickup means, the phase changes being random relative to each other, means coupled to the pickup means for combining selected relative amplitudes of the reproduced electrical signals to form a composite signal, means coupled to the signal combining means for applying the composite signal to the recording means whereby a reentrant loop is established within which the electrical signals circulate with both a delay and continuously variable phase shift being introduced with each passage of the electrical signals from the recording means to the recording medium and from the recording medium to each of the pickup means, a signal attenuator coupled to the reentrant loop for establishing the rate of attenuation of signals circulating within the loop, and a second signal channelcoupled to the reentrant loop for reproducing the composite signal whereby artificial reverberation and ensemble effects are produced through a simultaneous reproduction of the composite signal and the electrical signal from the electronic organ.

12. A magnetic recording device for use in conjunction with an electronic organ in generating special musical effects including the combination of a magnetic tape, means transporting the tape around a loop at an irregular rate, a recording head positioned adjacent the magnetic tape for initially recording signals derived from the electronic organ on the tape, a plurality of pickup heads spaced along the tape in a position trailing the recording head for producing electrical signals corresponding to the recorded signals on the tape, an attenuator, an amplifier connected serially with the attenuator between the pickup heads and the recording head to define a reentrant loop including the pickup heads. and recording head within which signals recorded by the recording head are circulated with variations in the velocity of the transport of the tape producing successively randomly varying phase changes in the signals being circulated, and means coupled to the reentrant loop for controlling the level of the circulating signals for the creation of special musical efiects.

13. Apparatus in accordance with claim 12, wherein the tape transporting means includes a rotating capstan having a rotational speed corresponding to vibrato, and including also means for periodically varying the rotational speed of the capstan at a predetermined rate to achieve special music eflects.

14. A magnetic recording device for use in conjunction with an electronic organ for the production of special musical effects which are dependent upon the velocity of transport of a magnetic recording medium including the combination of an endless tape, a tape transport mechanism comprising a motor, a capstan driving the tape, a pair of drive belts linked between the motor and the capstan, means for periodically braking the capstan to vary the velocity of transport of the tape, means for selectively and periodically altering the speed of the motor for varying the tape velocity, means for recording signals on the tape, and pickup means for deriving signals from the tape having variable characteristics attributable to variations in velocity of transport of the magnetic tape.

15. Apparatus in accordance with claim 14 in which the rotational speed of the capstan is selected to correspond to a vibrato musical effect.

16. Apparatus in accordance with claim 14 in which an amplifier and attenuator are connected serially between the pickup means and the recording head to establish a reentrant loop in which a variable delay is introduced by the passage of the magnetic tape between the recording head and the pickup means.

17. A magnetic recorder for use in conjunction with an electronic organ for the creation of special musical efiects including the combination of an endless length of magnetic tape, a pulley about which the tape travels, a capstan engaging two oppositely moving surfaces of the tape to form a loop between the capstan and the pulley, means rotating the capstan at a velocity which imparts variations in the velocity of transport of the tape corresponding to the speed of a musical vibrato, a first idler pulley for engaging the moving tape with one side of the capstan, said first idler pulley having a predetermined diameter, a second idler pulley engaging the moving tape with the opposite side of the capstan, said second idler pulley having a diameter differing from said predetermined diameter by at least ten percent, a recording head positioned adjacent the loop for recording electrical signals on the magnetic tape, a plurality of pickup heads mounted adjacent the loop trailing the recording head, each of said pickup heads being adapted to derive an electrical signal corresponding to the signals recorded upon the tape with the electrical signals having variable characteristics produced by variations in velocity of movement of the tape, an amplifier, an attenuator coupled serially with the amplifier between the pickup heads and the recording head whereby a rcentrant loop is established within which electrical signals are circulated between the pickup heads and the recording head with the moving magnetic tape affording a variable delay in phase shift of the signals within the reentrant loop, and means for simultaneously reproducing electrical signals circulating within the reentrant loop and the electrical signals being recorded by the recording head whereby special musical effects are produced by the interaction between the signals circulating within the reentrant loop and the signals being recorded.

18. Apparatus in accordanc with claim 17 including means coupled to the plurality of pickup heads for fixing relative selected amplitudes of the signals produced by each of the heads for passage to the amplifier and circulation within the reentrant loop.

19. Apparatus in accordance with claim 17 including selectively operable erasing means positioned adjacent the moving magnetic tape for removing signals recorded thereon.

20. In an electronic organ in which electrical signals are generated representing musical notes, means for creating artificial ensemble and reverberation elfects including the combination of a first signal channel for reproducing directly electrical signals produced by the organ, a continuously movable recording medium, means tor transporting the recording medium at a predetermined nominal velocity with minor random variations from the nominal velocity, a recording means positioned along the path of travel of the recording medium and adapted to record electrical signals derived from the organ, a plurality of pickup means positioned along the path of travel of the recording medium trailing the recording means, each of said pickup means being adapted to generate an electrical signal representing the recorded signals on the recording means, said pickup means being spaced apart whereby the recorded signals passing adjacent thereto produce successively in each of the pickup means an electrical signal which is delayed with respect to the electrical signal applied to the recording means with the minor variations in the velocity of transport of the recording medium producing randomly varying phase changes in the electrical signals produced by each of the pickup means, means coupled to the pickup means for combining selected relative amplitudes of the reproduced electrical signals to form a composite signal, means coupled to the signal combining means for applying the composite signal to the recording means whereby a reentrant loop is established within which the electrical signals circulate with a delay and variable phase shift being introduced with each passage of the electrical signals from the recording means to the recording medium and from the recording medium to the pickup means, a signal attenuator coupled to the reentrant loop for establishing the rate of attenuation of signals circulating within the loop, switching means for selectively altering the rate of attenuation within the loop, and a second signal channel coupled to the reentrant loop for reproducing the composite signal whereby the signals circulating within the loop are sustained to produce a sustained tone in the first signal channel which is extinguished by operation of said switching means to alter the rate of attenuation within the loop,

21. A magnetic recorder for use in conjunction with an electronic organ for the creation of special musical effects including the combination of an endless length of magnetic tape, a curved surface about which the tape travels, capstan means engaging two oppositely moving surfaces of the tape to form a loop between the capstan means and the curved surface, means rotating the capstan means at a velocity which imparts variations in the velocity of transport of the tape corresponding to the speed of a musical vibrato, at least one roller means engaging the moving tape with the capstan means, a recording head positioned adjacent the loop for recording electrical signals on the magnetic tape, multiple pickup means mounted adjacent the loop trailing the recording head, each of the pickup means deriving an electrical signal corresponding to the signals recorded on the tape, means coupled serially between the pickup means and the recording head for establishing a reentrant loop within which electrical signals are circulated, and means for simultaneously reproducing electrical signals circulating within the reentrant loop and the electrical signals being recorded by the recording head whereby special acoustical musical efiects may be produced through concurrent use of the signals circulating within the reentrant loop and the signals being recorded.

References Cited in the file of this patent UNITED STATES PATENTS 325,699 Stille May 21, 1930 2,141,231 Trautwein Dec. 27, 1938 2,327,956 Begun Aug. 24, 1943 2,354,176 Goldsmith July 18, 1944 2,512,015 Graviel June 20, 1950 2,645,969 Daniels July 21, 1953 2,674,660 Ambrose Apr. 6, 1954 2,748,192 Goodfriend May 29, 1956 2,767,254 Laiferty Oct. 16, 1956 2,821,878 Stibitz Feb. 4, 1958 2,843,676 Halliday July 15, 1958 2,872,515 Goldmark Feb. 3, 1959 3,004,459 Jones Oct. 17, 1961 

11. IN AN ELECTRONIC ORGAN IN WHICH ELECTRICAL SIGNALS ARE GENERATED REPRESENTING MUSICAL NOTES, MEANS FOR CREATING ARTIFICIAL ENSEMBLE AND REVERBERATION EFFECTS INCLUDING THE COMBINATION OF A FIRST SIGNAL CHANNEL FOR REPRODUCING DIRECTLY ELECTRICAL SIGNALS PRODUCED BY THE ORGAN, A CONTINUOUSLY MOVABLE RECORDING MEDIUM, MEANS FOR TRANSPORTING THE RECORDING MEDIUM WITH VELOCITIES WHICH CONTINUOUSLY VARY OVER A PHASE RESPONSIVE RANGE FROM A PREDETERMINED NOMINAL VELOCITY, A RECORDING MEANS POSITIONED ALONG THE PATH OF TRAVEL OF THE RECORDING MEANS AND RECORDING ELECTRICAL SIGNALS DERIVED FROM THE ORGAN WITH CONTINUOUSLY VARYING PHASE CHANGES, A PLURALITY OF PICKUP MEANS POSITIONED ALONG THE PATH OF TRAVEL OF THE RECORDING MEDIUM TRAILING THE RECORDING MEANS, EACH OF SAID PICKUP MEANS GENERATING AN ELECTRICAL SIGNAL REPRESENTING THE RECORDED SIGNALS ON THE RECORDING MEANS, SAID PICKUP MEANS BEING SPACED APART WHEREBY THE RECORDED SIGNALS PASSING ADJACENT THERETO PRODUCE SUCCESSIVELY IN EACH OF THE PICKUP MEANS AN ELECTRICAL SIGNAL WHICH IS DELAYED WITH RESPECT TO THE ELECTRICAL SIGNAL APPLIED TO THE RECORDING MEANS WITH VARIATIONS IN THE VELOCITY OF TRANSPORT OF THE RECORDING MEDIUM PRODUCING ADDITIONAL AND RANDOMLY VARYING PHASE CHANGES IN THE ELECTRICAL SIGNALS PRODUCED BY EACH OF THE PICKUP MEANS, THE PHASE CHANGES BEING RANDOM RELATIVE TO EACH OTHER, MEANS COUPLED TO THE PICKUP MEANS FOR COMBINING SELECTED RELATIVE AMPLITUDES OF THE REPRODUCED ELECTRICAL SIGNALS TO FORM A COMPOSITE SIGNAL, MEANS COUPLED TO THE SIGNAL COMBINING MEANS FOR APPLYING THE COMPOSITE SIGNAL TO THE RECORDING MEANS WHEREBY A REENTRANT LOOP IS ESTABLISHED WITHIN WHICH THE ELECTRICAL SIGNALS CIRCULATE WITH BOTH A DELAY AND CONTINUOUSLY VARIABLE PHASE SHIFT BEING INTRODUCED WITH EACH PASSAGE OF THE ELECTRICAL SIGNALS FROM THE RECORDING MEANS TO THE RECORDING MEDIUM AND FROM THE RECORDING MEDIUM TO EACH OF THE PICKUP MEANS, A SIGNAL ATTENUATOR COUPLED TO THE REENTRANT LOOP FOR ESTABLISHING THE RATE OF ATTENUATION OF SIGNALS CIRCULATING WITHIN THE LOOP, AND A SECOND SIGNAL CHANNEL COUPLED TO THE REENTRANT LOOP FOR REPRODUCING THE COMPOSITE SIGNAL WHEREBY ARTIFICIAL REVERBERATION AND ENSEMBLE EFFECTS ARE PRODUCED THROUGH A SIMULTANEOUS REPRODUCTION OF THE COMPOSITE SIGNAL AND THE ELECTRICAL SIGNAL FROM THE ELECTRONIC ORGAN. 